Hydraulic lifting devices of tractors



Nov. 10, 1964 1.. PERAS 3,156,156

HYDRAULIC LIFTING DEVICES OF TRACTORS Filed Aug. 10, 1959 2 Sheets-Sheet 1 Fllg. I

Nov. 10, 1964 PERAS 3,1

HYDRAULIC LIFTING DEVICES 0F TRACTORS Filed Aug. 10, 1959 2 Sheets-Sheet 2 Fly. 4

Fig. 5

United States Patent 3,156,156 HYDRAULIU LIFTING DEVICES 0F TRACTGRS Lucien Pras, li-iliancourt, France, assignor to Regie Nationals des Usiues Renault, llillancourt, France Filed Aug. 10, 1959, Ser. No. 832,814 Claims priority, application France, Sept. 8, 1958, 774,018, Patent 1,222,459 Claims. (Ci. 91-31) The present invention is concerned with a hydraulic lifting device for farming and like tractors, this device being designed more specifically for equipping tractors having a so-called Universal coupling or a well-known three-point coupling.

The essential object of this invention is to provide a device of this character which constitutes a simple and reliable system of maintaining at a constant preselected level the points where the farming equipments are coupled to the drawing rods or arms irrespective of the movements and stress applied by the ground surface to the towed equipment.

It is another feature of the device of this invention to incorporate a control lever of which the different positions correspond to predetermined positions of the points of coupling of the towed equipment, the device being of the so-called pre-setting type.

With these two essential features it is extremely easy for the operator to obtain a constant depth of operation of the towed equipment in successive fields.

With the device of this invention it is also possible to transfer at will to the rear axle of the tractor one portion of the weight of the equipment coupled thereto, so that in difficult circumstances the adherence of the driving wheels of the tractor and therefore its tractive force can be increased considerably.

Finally, this device constitutes a practical and simple means whereby one or more auxiliary hydraulic cylinders, jacks, or rams can be fed with fluid under pressure.

A typical form of embodiment of a hydraulic lifting device according to this invention will now be described by way of example with reference to the attached drawings forming part of this specification. In the drawings:

FIGURE 1 is a diagrammatic elevational and sectional view showing the essential component elements of the device of this invention shown in its stabilized position with the hydraulic circuit by-passed;

FIGURE 2 is a similar view of the device showing its operation when the control lever is moved to its position demanding the lifting of the drawing arm;

FIGURE 3 is a similar view showing the operation of the device when the control lever is moved to its position demanding the lowering of the lifting arm;

FIGURE 4 is a similar view showing the operation of the so-called modulation device when it is desired to transfer one fraction of the coupled equipment to the tractor; and

FIGURE 5 is similar view showing the operation of the device when it is desired to supply fluid under pressure to auxiliary hydraulic cylinders, jacks or rams.

Referring firstly to FIG. 1 of the drawings, the hydraulic lifting device of this invention comprises a fluidfilled sump 1 having immersed therein the inlet end of the pipe 2 for supplying the hydraulic circuit with fluid forced therethrough by a pump 3 driven from the tractor through means not shown, this hydraulic circuit being adapted, through a distributor designated as a whole by the reference numeral 4, to supply fluid under pressure to a single-acting lifting cylinder 5 having its piston 6 connected through a connecting-rod 7 to a bell-crank lever fulcrumed on a pin 3 and having a rear arm 9 constituting the arm for lifting the equipment (not shown) coupled to the tractor.

The distributor 4 comprises a control slide or pilot valve 10 connected in the known manner through linkage means 11 both to the lifting arm 9 and to the control lever 12 whereby the operator may control at will the upward and downward movements of this arm 9.

The slide valve ll) constitutes a double piston and the piston body lll controls the passage of derivated fluid which takes place in this example through a groove or exhaust port 13 formed in the wall of the slide-valve cylinder at the outlet end of a chamber 14 branched off the distribution circuit and supplied with fluid under pressure through a throttled passage 15. The pressure developing in this chamber 14- when the passage 13 is closed is available for actuating through the medium of a piston 16 a by-pass valve 17.

Downstream of by-pass Valve 17 is an outlet valve 18 also constituting under normal conditions of operation a non-return valve in relation to the lifting cylinder 5 fed through the pipe line 19.

Under specific conditions to be set forth presently, this valve 13 can be kept positively open by means of a push-member 26 adapted to be actuated by the other piston body 10 of the slide-valve which, in this case, will act as a cam controlling this outlet valve.

Moreover, downstream of the outlet valve 13 is a nozzle adjustable by means of a needle or metering valve 2 1, and downstream of this nozzle is a branch pipe 22 connecting the circuit feed line 2 to the outlet pipe I? loading to a servo-cylinder 5, a non-return valve 23 being interposed therein. Mounted in the feed line 2, after the branch pipe 22 and before the distributor is a valve 24 whereby the cross-sectional area available for the passage of the fluid may be modified at will within limits corresponding to the function to be set forth presently in the part of the description dealing with the operation of the device. Completely upstream of the feed pipe 2 is a relief valve 25' provided in this example, for the sake of safety, with a control rod 26 adapted to be actuated by the movable member 6 of cylinder 5 when the maximum lifting position not to be overstepped is attained.

Finally, there is provided completely downstream of all other controls a three-way cock 27 in pipe 1? adapted, when. it is desired to feed auxiliary cylinders, to isolate the lifting cylinder and to connect the circuit of these auxiliary cylinders through a branch pipe 29.

This lifting device operates as follows:

Due to the linkage system provided between the control slide valve 10 and the control lever 12 and lifting arm 9, to each position of the control lever there corresponds a given position of the lifting arm wherein the piston body 10 of the slide valve closes the branch passage 13 and causes the circuit to be thus by-passed, as illustrated in FIG. 1 for the lower position of the lifting arm, but this by-passing will be seen again in a later part of the description dealing with the arm raising and lowering movements. This by-passing results from the action exerted by the fluid under pressure in chamber 14 against a servo-piston 16 which causes the by-pass valve 17 to open, so that the fluid will flow in the direction of the arrows shown in FIG. 1, the fluid being returned to the sump through this valve under a certain pressure.

The operation in case of a demand for a lifting movement is illustrated in PEG. 2. When the control lever 12 is pulled to the rear, the linkage 11 bears against the lifting arm so as to move the slide valve 10 forwards, this step being illustrated in the drawing. The passage 13 is then open to the sump and the pressure drops in chamber 14, so that the by-pass valve 17 is reseated immediately. The fluid under pressure will then unseat the valves 18 and 23 and enter into the cylinder 5, thus causing the upward movement of the arm 9, the fluid circulating along the path shown by the arrows.

Then, the arm 9 causes the slide valve 10 to resume its initial position; to do this, the arm 9 engages the linkage 11 bearing now on the control lever 12 locked in a given position. When the slide 10 has again closed the passage 13, the circuit is by-passed as already described, and the lifting arm 9 is held in a stable position since the valves 18 and 23 will then prevent any fluid from flowing back from the cylinder 5. During the upward movement, a moderate flow takes place through the throttle orifice 15, and the dimension of this orifice is so selected as to avoid any unduly long lifting time for the highest possible fluidity of the hydraulic medium.

The operation obtaining in case of a demand for a lowering movement from the upper position of the lifting arm is shown in FIG. 3. By moving the control lever 12 forwards, the slide valve 10 will move to the rear as shown in the drawing. As in this case the passage 13 is not open in the direction of the sump, the by-pass valve 17 remains open and the piston body 10 causes the valve 18 to open by engaging the push member 20. The fluid hitherto trapped by this valve for maintaining the lifting arm in the requisite position is then forced to the sump through the by-pass valve as indicated by the arrows but must pass through the nozzle 21 controlled by the adjustable needle valve, the latter having actually the function of permitting the adjustment of the arm-lowering movement. With this arrangement it is thus possible to obtain variable lowering speeds for a same equipment coupled to the tractor, or the same speed with equipments having very different weights. The lifting arm, as it is lowered, restores the slide valve 10 to its initial position and the downward movement is discontinued when the piston body 10 allows the push-member r to re-close the valve 18, whereafter the circuit remains only in its by-pass condition.

FIG. 4 illustrates the so-called modulation operation obtaining when, for the reason already set forth, it is desired to transfer to the rear axle of the tractor one fraction of the weight of the machine coupled thereto.

Irrespective of the position of the lifting arm 9 which may have been preset by means of the control lever 12, and if the valve 24 is actuated with a view to reduce the cross-sectional area available for the passage of fluid, the fluid pressure in the circuit portion located upstream of this valve will be increased and transmitted to the lifting cylinder as a consequence of the opening of valve 23.

The reduction in the cross-sectional area which is caused by this modulating valve 24 is so determined that the increased fluid pressure which can thus be applied to the lifting cylinder will not exceed that resulting from the weight of the equipment coupled to the tractor. Consequently, upon actuating this valve, this equipment will be relieved since one fraction of its weight will be transferred to the driving wheels of the tractor, as required, but without being raised. This valve is to be operated only temporarily and therefore a return member will be associated therewith to urge the valve to its normal through-flow position (full cross-sectional area of its passage).

The operation of the arrangement for supplying pressurized fluid to auxiliary cylinders is illustrated in FIG. 5.

The three-way cock 27 is set in the proper position for isolating the main cylinder circuit in any desired position of the lifting arm 9, while connecting the pressure side of the circuit to the pipe 28 for supplying fluid under pressure to the auxiliary cylinder or cylinders, for example a ram or hydraulic jack.

Since after the actuation of the cock 27, the circuit remains in its by-pass condition, the control lever 12 must then be operated in the proper direction to raise the arm 9, as shown in the figure, in order to eliminate the by-pass flow of fluid by displacing the slide valve 10 forwards with a view to cause a forced feeding of the device connected to the pipe line 28.

Then the fluid flow takes place along the path shown by the arrows in this figure. The stabilization position, for example when a hydraulic lifting cylinder is operated, is obtained by restoring manually the control lever 12 to its initial position causing the by-passing of the hydraulic circuit due to the movement of the slide valve to the corresponding position. Similarly, the operation in the arm-lowering direction is obtained in the same manner as that described, by moving the control lever 12 forwards in relation to its by-pass setting position indicating the position in which the lifting arm has been retained.

Of course, various modifications and alterations may be brought to the specific form of embodiment shown and described herein without departing from the spirit and scope of the invention as set forth in the appended claims.-

I claim:

1. In a tractor having a hitch for connecting an implement thereto and a hydraulic control system having a manual control lever for controlling said system for raising and lowering the hitch, said system including a fluid ram connected to the hitch, a fluid circuit comprising a pump, a reservoir, and a distributor comprising a pilot valve having a neutral position and operable from said neutral position in opposite directions to extreme operative positions for controlling the action of said fluid on said fluid ram, means defining two parallel flow paths in said fluid circuit connecting said pump with said fluid ram, one of said flow paths being connected between said pump and fluid ram and including a first non-return valve, a second flow-path of said two flow-paths connected to said one flow path upstream of said first non-return valve and downstream thereof comprising a throttle valve and a second non-return valve biased to a closed position and serially connected with said throttle valve, a by-pass valve biased to a closed position and in communication with said second flow path upstream of said second non-return valve to bypass the fluid to said reservoir, follow-up linkage connecting said pilot valve to the hitch and activated by said ram for positioning said pilot valve in said neutral position and connected to said manual control lever for positioning said pilot valve in said extreme positions, said bypass valve being controlled by said pilot valve and being open at the positioning of said pilot valve in said neutral position, said control lever being operable to two operative positions for controlling the movement of said pilot valve, in one direction to an extreme position for controlling the closing of said by-pass valve thereby to supply fluid under pressure to the fluid ram and in another direction to another extreme position for opening said second non-return valve and said by-pass valve to allow discharge of said fluid from said ram, and said throttle valve having means operable selectively to restrict the flow through said second flow path for increasing the pressure upstream of said by-pass valve to apply to the fluid ram an increased pressure tending to elevate said hitch to effect a transfer of a fraction of the load on the implement to said hitch.

2. In a tractor having a hitch for connecting an implement thereto and a hydraulic control system having a manual control lever for controlling said system for raising and lowering the hitch, said system including a fluid ram connected to the hitch, a fluid circuit comprising a pump, a reservoir, and a distributor comprising a pilot valve having a neutral position and operable from said neutral position in opposite directions to extreme operative positions for controlling the action of said fluid on said fluid ram, means defining two parallel flow paths in said fluid circuit connecting said pump with said fluid ram, one of said flow paths being connected between said pump and fluid ram and including a first non-return valve, a second flow-path of said two flow-paths connected to said one flow path upstream of said first non-return valve and downstream thereof comprising a throttle valve and a second non-return valve biased to a closed position and serially connected with said throttle valve, a by-pass valve biased to a closed position and in communication with said second flow path upstream of said second non-return valve to bypass the fluid to said reservoir, follow-up linkage connecting said pilot valve to the hitch and activated by said ram for positioning said pilot valve in said neutral position and connected to said manual control lever for positioning said pilot valve in said extreme positions, said by-pass valve being controlled by said pilot valve and being open at the positioning of said pilot valve in said neutral position, said control lever being operable to two operative positions for controlling the movement of said pilot valve, in one direction to an extreme position for controlling the closing of said by-pass valve thereby to supply fluid under pressure to the fluid ram and in another direction to another extreme position for opening said second non-return valve and said by-pass valve to allow discharge of said fluid from said ram, said throttle valve having means operable selectively to restrict the flow through said second flow path for increasing the pressure upstream of said by-pass valve to apply as to the fluid ram an increased pressure tending to elevate said hitch to effect a transfer of a fraction of the load on the implement to said hitch, and said pilot valve comprising cam means for actuating said second non-return valve to an open position when in said another extreme position.

3. In a tractor having a hitch for connecting an implement thereto and a hydraulic control system having a manual control lever for controlling said system for rais ing and lowering the hitch, said system including a fluid ram connected to the hitch, a fluid circuit comprising a pump, a reservoir, and a distributor comprising a pilot valve having a neutral position and operable from said neutral position in opposite directions to extreme operative positions for controlling the action of said fluid on said fluid ram, means defining two parallel flow paths in said fluid circuit connecting said pump with said fluid ram, one of said flow paths being connected between said pump and fluid ram and including a first non-return valve, a second flow-path of said two flow-paths connected to said one flow path upstream of said first non-return valve and downstream thereof comprising a throttle valve and a second non-return valve biased to a closed position and serially connected with said throttle valve, a bypass valve biased to a closed position and in communication with said second flow path upstream of said second non-return valve to bypass the fluid to said reservoir, follow-up linkage connecting said pilot valve to the hitch and activated by said ram for positioning said pilot valve in said neutral position and connected to said manual control lever for positioning said pilot valve in said extreme positions, said by-pass valve being controlled by said pilot valve and being open at the positioning of said pilot valve in said neutral position, said control lever being operable to two operative positions for controlling the movement of said pilot valve, in one direction to an extreme position for controlling the closing of said bypass valve thereby to supply fluid under pressure to the fluid ram and in another direction to another extreme position for opening said second non-return valve and said by-pass valve to allow discharge of said fluid from said ram, said throttle valve having means operable selectively to restrict the flow through said second flow path for increasing the pressure upstream of said by-pass valve to apply to the fluid ram an increased pressure tending to elevate said hitch to etfect a transfer of a fraction of the load on the implement to said hitch, said distributor having a chamber in communication with said second flow path and an exhaust port in communication with said reservoir and said chamber and closed by said pilot valve when in said neutral position, and a servo-piston connected to said bypass valve and actuated in response to pressure in said chamber for opening said bypass valve.

4. In a tractor having a hitch for connecting an implcment thereto and a hydraulic control system having a manual control lever for controlling said system for raising and lowering the hitch, said system including a fluid ram connected to the hitch, a fluid circuit comprising a pump, a reservoir, and a distributor comprising a pilot valve having a neutral position and operable from said neutral position in opposite directions to extreme operative positions for controlling the action of said fluid on said fluid ram, means defining two parallel flow paths in said fluid circuit connecting said pump with said fluid ram, one of said flow paths being connected between said pump and fluid ram and including a first non-return valve, a second flow-path of said two flow-paths connected to said one flow path upstream of said first nonreturn valve and downstream thereof comprising a throttle valve and a second non-return valve biased to a closed position and serially connected with said throttle valve, a by-pass valve biased to a closed position and in communication with said second flow path upstream of said second non-return valve to bypass the fluid to said reservoir, follow-up linkage connecting said pilot valve to the hitch and activated by said ram for positioning said pilot valve in said neutral position and connected to said manual control lever for positioning said pilot valve in said extreme positions, said by-pass valve being controlled by said pilot valve and being open at the positioning of said pilot valve in said neutral position, said control lever being operable to two operative positions for controlling the movement of said pilot valve, in one direction to an extreme position for controlling the closing of said bypass valve thereby to supply fluid under pressure to the fluid ram and in another direction to another extreme position for opening said second non-return valve and said by-pass valve to allow discharge of said fluid from said ram, said throttle valve having means operable selectively to restrict the flow through said second flow path for increasing the pressure upstream of said by-pass valve to apply to the fluid ram an increased pressure tending to elevate said hitch to effect a transfer of a fraction of the load on the implement to said hitch, said distributor having a chamber in communication with said second flow path and an exhaust port in communication with said reservoir and closed by said pilot valve when in said neutral position, a servo-piston connected to said bypass valve actuated in response to pressure in said chamber for opening said by-pass valve, and said pilot valve comprising cam means for actuating said second nonreturn valve to an open position when in said another extreme position.

5. In a tractor having a hitch for connecting an implement thereto and a hydraulic control system having a manual control lever for controlling said system for raising and lowering the hitch, said system including a fluid ram connected to the hitch, a fluid circuit comprising a pump, a reservoir, and a distributor comprising a pilot valve having a neutral position and operable from said neutral position in opposite directions to extreme operative positions for controlling the action of said fluid on said fluid ram, means defining two parallel flow paths in said fluid circuit connecting said pump with said fluid ram, one of said flow paths being connected between said pump and fluid ram and including a first non-return valve, a second flow-path of said two flowpaths connected to said one flow path upstream of said first non-return valve and downstream thereof comprising a throttle valve and a second non-return valve biased to a closed position and serially connected with said throttle valve, a metering valve in said second flow-path downstream of said second non-return valve, a by-pass valve biased to a closed position and in communication with said second flow path upstream of said second nonreturn valve to bypass the fluid to said reservoir, followup linkage connecting said pilot valve to the hitch and activated by said ram for positioning said pilot valve in said neutral position and connected to said manual control lever for positioning said pilot valve in said extreme positions, said by-pass valve being controlled by said pilot valve and being open at the positioning of said pilot valve in said neutral position, said control lever being operable to two operative positions for controlling the movement of said pilot valve, in one direction to an extreme position for controlling the closing of said by-pass valve thereby to supply fluid under pressure to the fluid ram and in another direction to another extreme position for opening said second non-return valve and said bypass valve to allow discharge of said fluid from said ram, said throttle valve having means operable selectively to restrict the flow through said second flow path for increasing the pressure upstream of said by-pass valve to apply to the fluid ram an increased pressure tending to elevate said hitch to effect a transfer of a fraction of the load on the implement to said hitch, said distributor having a chamber in communication with said second flow path and an exhaust port in communication with said reservoir and closed by said pilot valve when in said neutral position, a servo-piston connected to said by-pass valve and actuated in response to pressure in said chamber for opening said by-pass valve, and said pilot valve comprising cam means for actuating said second non-return valve to an open position when in said another extreme position.

References Cited in the file of this patent UNITED STATES PATENTS 2,375,946 Reichelt May 15, 1945 2,477,710 Worstell Aug. 2, 1949 2,482,249 Court Sept. 20, 1949 2,538,143 Brown Jan. 16, 1951 2,847,030 McRae Aug. 12, 1958 2,851,938 Giertz et al. Sept. 16, 1958 

1. IN A TRACTOR HAVING A HITCH FOR CONNECTING AN IMPLEMENT THERETO AND A HYDRAULIC CONTROL SYSTEM HAVING A MANUAL CONTROL LEVER FOR CONTROLLING SAID SYSTEM FOR RAISING AND LOWERING THE HITCH, SAID SYSTEM INCLUDING A FLUID RAM CONNECTED TO THE HITCH, A FLUID CIRCUIT COMPRISING A PUMP, A RESERVOIR, AND A DISTRIBUTOR COMPRISING A PILOT VALVE HAVING A NEUTRAL POSITION AND OPERABLE FROM SAID NEUTRAL POSITION IN OPPOSITE DIRECTIONS TO EXTREME OPERATIVE POSITIONS FOR CONTROLLING THE ACTION OF SAID FLUID ON SAID FLUID RAM, MEANS DEFINING TWO PARALLEL FLOW PATHS IN SAID FLUID CIRCUIT CONNECTING SAID PUMP WITH SAID FLUID RAM, ONE OF SAID FLOW PATHS BEING CONNECTED BETWEEN SAID PUMP AND FLUID RAM AND INCLUDING A FIRST NON-RETURN VALVE, A SECOND FLOW-PATH OF SAID TWO FLOW-PATHS CONNECTED TO SAID ONE FLOW PATH UPSTREAM OF SAID FIRST NON-RETURN VALVE AND DOWNSTREAM THEREOF COMPRISING A THROTTLE VALVE AND A SECOND NON-RETURN VALVE BIASED TO A CLOSED POSITION AND SERIALLY CONNECTED WITH SAID THROTTLE VALVE, A BY-PASS VALVE BIASED TO A CLOSED POSITION AND IN COMMUNICATION WITH SAID SECOND FLOW PATH UPSTREAM OF SAID SECOND NON-RETURN VALVE TO BYPASS THE FLUID TO SAID RESERVOIR, FOLLOW-UP LINKAGE CONNECTING SAID PILOT VALVE TO THE HITCH AND ACTIVATED BY SAID RAM FOR POSITIONING SAID PILOT VALVE IN SAID NEUTRAL POSITION AND CONNECTED TO SAID MANUAL CONTROL LEVER FOR POSITIONING SAID PILOT VALVE IN SAID EXTREME POSITIONS, SAID BYPASS VALVE BEING CONTROLLED BY SAID PILOT VALVE AND BEING OPEN AT THE POSITIONING OF SAID PILOT VALVE IN SAID NEUTRAL POSITION, SAID CONTROL LEVER BEING OPERABLE TO TWO OPERATIVE POSITIONS FOR CONTROLLING THE MOVEMENT OF SAID PILOT VALVE, IN ONE DIRECTION TO AN EXTREME POSITION FOR CONTROLLING THE CLOSING OF SAID BY-PASS VALVE THEREBY TO SUPPLY FLUID UNDER PRESSURE TO THE FLUID RAM AND IN ANOTHER DIRECTION TO ANOTHER EXTREME POSITION FOR OPENING SAID SECOND NON-RETURN VALVE AND SAID BY-PASS VALVE TO ALLOW DISCHARGE OF SAID FLUID FROM SAID RAM, AND SAID THROTTLE VALVE HAVING MEANS OPERABLE SELECTIVELY TO RESTRICT THE FLOW THROUGH SAID SECOND FLOW PATH FOR INCREASING THE PRESSURE UPSTREAM OF SAID BY-PASS VALVE TO APPLY TO THE FLUID RAM AN INCREASED PRESSURE TENDING TO ELEVATE SAID HITCH TO EFFECT A TRANSFER OF A FRACTION OF THE LOAD ON THE IMPLEMENT TO SAID HITCH. 